A known seat apparatus is disclosed in JP2003-182415A (hereinafter referred to as Patent reference 1). According to Patent reference 1, the seat apparatus includes a lower arm which is provided at a seat cushion and an upper arm which is provided at a seatback. Because the upper arm is pivotally connected to the lower arm via a pin, the upper arm pivots in a front-rear direction via the pin. A pivot member is fixed to the upper arm so as to integrally pivotally move therewith. A first link is pivotally connected to the lower arm via the pin. A first end of the first link is attached with a contact pin. A second end of the first link is linked with a lock member which selectively restricts the movement of a seat in the front-rear direction. The contact pin is disposed on a pivot trajectory of the pivot member when the upper arm pivots forward. Thus, when the seatback moves from an occupied state to a forward-inclined state (hereinafter referred to as forward inclination), the lock member allows the movement of the seat in the front-rear direction because the first link is pressed by the pivot member and pivots. Accordingly, the seat moves in the front-rear direction in connection with the forward inclination of the seatback.
A seat reclining apparatus is disclosed in JP2009-82241A (hereinafter referred to as Patent reference 2). The seat reclining apparatus includes a lower arm and an upper arm. Respective pivot centers of the lower arm and the upper arm are eccentric from each other to adjust and hold an inclination angle of a seatback relative to a seat cushion. In particular, the seat reclining apparatus is provided with, for example, an internal gear, an external gear, a wedge member and a cam shaft. The internal gear is formed at the lower arm. The external gear includes teeth fewer than the teeth of the internal gear and is formed at the upper arm. The wedge member holds the internal gear and the external gear eccentrically to engage the internal gear with the external gear. The cam shaft is disposed coaxially with the lower arm (internal gear) and axially supports the upper arm. The cam shaft moves the wedge member. By the movement of the wedge member in response to the rotation of the cam shaft, the upper arm revolves while the wedge member holds the internal gear and the external gear meshed with each other to decrease the rotary speed of the cam shaft which corresponds to the rotation of the upper arm during the revolving. Then the seatback pivots (is inclined) relative to the seat cushion by the rotation of the upper arm relative to the lower arm.
In a case where the seat apparatus includes a structure in which the pivot centers of the lower arm and the upper arm are eccentric from each other, when the seat back is inclined forward, the pivot member presses the first link (the contact pin) in a state where the upper arm is eccentric from the lower arm. Accordingly, the lock member which is linked with the first link does not securely allow the movement of the seat.
A need thus exists for a seat apparatus which is not susceptible to the drawback mentioned above.